#include <iostream>
#include <algorithm>
#include <vector>
#include <cstdio>
#include <cmath>

struct pos_time { int p, t; };

bool operator<(pos_time a, pos_time b)
{
	return a.t < b.t;
}

std::vector<pos_time> da;
int n;

int main()
{
	int T;
	std::cin >> T;
	for (int ti = 1; ti <= T; ti++) {
		std::cout << "Case #" << ti << ": ";

		std::cin >> n;
		da.resize(n);
		for (int i = 0; i < n; i++)
			std::cin >> da[i].t >> da[i].p;
		std::sort(da.begin(), da.end());
		double max_speed = 0;
		for (int i = 1; i < (int)da.size(); i++)
			max_speed = std::max(max_speed,
					std::abs(double(da[i].p - da[i-1].p))/double(da[i].t - da[i-1].t));
		std::printf("%.2f\n", max_speed);
	}
}
